1. Technical Field
The present invention is related to a linear vibration generator.
2. Description of the Related Art
A vibration motor is a part that converts electrical energy into mechanical vibrations by using the principle of generating electromagnetic forces, and is commonly installed in a mobile terminal, such as a mobile phone and a PDA, to generate a soundless vibrating alert. With the rapid expansion of mobile terminal markets and increased functionalities added to the mobile terminal, the mobile terminal is increasingly required to be smaller and better. As a result, there has been an increased demand for the development of a new structure of vibration motor that can overcome the shortcoming of conventional vibration motors and effectively improve the quality.
As mobile terminals having a bigger LCD screen have become popular for the past few years, there have been an increasing number of mobile terminals adopting a touch-screen method, by which the body or screen of a mobile terminal is vibrated when a user touches an input unit of the mobile terminal in order to provide the user an appealing sensory feel when touching the touch screen. Commonly used to generate the vibration is a vibration motor.
The touch-screen method particularly requires that the vibration motor has a greater durability due [[the]] to a greater frequency of generating vibrations in response to the touch compared to the vibration bell for incoming calls and that the vibration motor has a faster response to the touch made on the touch screen, in order to provide the user a greater satisfaction from sensing the vibration when touching the touch screen.
The conventional vibration motors commonly used in mobile phones generate a rotational force to cause mechanical vibrations by rotating an eccentric (unbalanced) rotor. The rotational force is generated by supplying an electric current to the coil of a rotor by using the rectifying action of a brush and a commutator.
The vibration motor using such brush and commutator has a shorter operating lifetime due to mechanical friction and electrical sparks, which cause wear and black powder, while the brush moves between the segments of the commutator when the motor rotates. Moreover, when voltage is supplied to the vibration motor, it takes time to reach the target amount of vibration, i.e., the magnitude by which it is sufficient for the user to sense the vibration, by the rotational inertia of the vibration motor, causing a slower response to the touch made on the touch screen.
Developed to overcome the drawbacks of shorter operating lifetime and slower responsiveness is a linear vibration generator. The linear vibration generator does not use the principle of rotation of a motor but uses an electromagnetic force having a predetermined resonant frequency to generate vibrations by use of a stationary part installed in the linear vibration generator and the mass of a vibrating part elastically supported to the stationary part by an elastic member.
In the linear vibration generator, however, the vibrating part may have friction with the stationary part due to shocks applied in a direction that is different from the linear direction of the vibrating part when the vibrating part vibrates. If the amplitude of the vibrating part becomes wider, the vibrating part may collide with the stationary part, causing noise.